Telegraph system



Jan. 25, 1938. T. A. MARSHALL TELEGRAPH SYSTEM 2 Sheets-:Sheef 1 Filed July 30, 1936 .ll ll. II IIII QEMG \ Min 1 m S um INVENTOR 7.,4. MARSHALL ATTORNEY Jan. 25; 1938.

T. A. MARSHALL TELEGRAPH SYSTEM Filed July 50, 1936 2 Sheets-Sheet 2 l l-l lNl/ENTOR 7.' A. MARSHALL Patented Jan. 25, 1938 UNITED STATES PATENT OFFICE Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application July 30, 1936, Serial No. 93,350

10 Claims.

This invention relates to telegraph systems and particularly to teletypewriter systems and it is the object of the invention to facilitate the testing and maintenance of teletypewriter switchboards.

In telegraph systems comprising a teletypewriter switchboard and a test board, it is known to provide one or more trunks between these boards for communication and to provide testmg trunks between these boards. In accordance with this invention a trunk is provided for communicating between a teletypewriter switchboard and a test board and this trunk is arranged for testing the cord circuits at the teletypewriter l5 switchboard.

One feature of the invention is a trunk between a telegraph switchboard and a test board arranged to employ -cyc1e ringing current for testing cord circuits.

, These and other features of the invention will be further described by considering a specific embodiment of the invention, one such embodiment being illustrated schematically in the drawings which form a part of this specification. While the switching equipment in the system shown is of the manually operated type, it is, of course, understood that this invention is applicable to systems employing automatic switching equipment.

Referring to the drawings Fig. 1 shows a test board comprising a two-way trunk circuit T, a test cord TC, a patching cord PC, a teletypewriter cord TTC, a teletyp'ewriter TTY, and teletypewriter jacks REC and send;

Fig. 2 shows a teletypewriter switchboard comprising a cord circuit C, an operators position circuit 0, and the jacks TRK and call-test to which the trunk T of Fig. 1 is connected.

The cord circuit C, which comprises the answer- 40 ing plug 5|, calling plug repeating relays 55 and 15, and teletypewriterkey 60, is one of a plurality provided at the operators position 0 for use in interconnecting subscribers loops .and telegraph lines. In addition to the call-test and TRK jacks 49 and 50 which terminate the trunk T from the test board, answering jacks and multiple jacks are provided for connecting with the subscribers loops and telegraph lines. The operators position 0 comprises sending contacts 80 and a receiving magnet 8|. For a complete description of the operation of similar cord circuits in establishing connectionsbetween subscribers loops and telegraph lines, reference may be had tcPatent 1,979,273, granted't o GHQ. Lane et al.; 56' November 6; 1934 andto application Serial No;

459,684, filed June '7, 1930 by G. A. Locke et al.

The trunk circuit T comprises sleeve relay 24 and'auxiliary relays and 26, an answering lamp 20 associated with the REC and TRK jack'Zl, a recall-reverse key 30, a reversing relay 3|, recall relay 32, a source of ZO-cycle ringing current 29, a relay 21 for establishing the circuit connections in the trunk for testing the bias of 20-cycle signals sent to and repeated back from a cord under test, a relay for receiving the bias test signals from the cord, a bias jack 22 for use in connecting the voltmeter of a test cord to the relay 35, and a send jack 23 for use in connecting the signal sending contacts of the teletypewriter or any other sending contacts to the trunk.

To describe the use and operation of the trunk T, assume firstthat a test man at the test board wishes to communicate with an operator at the switchboard. With the teletypewriter connected by plugs II and I3 andrjacks l4, l5 and Hi to 20 the teletypewriter cord TTC, the plug of cord TTC is inserted in the REC andTRK jack 2| thereby connecting the sending contacts I'll-and receiving magnet |2 in series with the conductor 42 of trunk T. At the upper contact of jack 2|, a circuit is closed for energizingthe upper winding of relay 26. Relay 26 operates and connects ground through its lowermost front contact and back contact of relay 25 over conductor 43 to the answering lamp 4! at the switchboard. Lamp 41 and the other lamps associated with multiple trunk jacks 5|! are lighted. The operation of rel-ay 26 closes a loop circuit through the teletypewriter; this circuit is traced from ground at the back contact of relay 24, through the upper front contact of relay 26, lower back contact of relay 21, sleeve conductors of jack 2| and cord TTC, upper back contact of jack l6, sleeve conductors of jack l5 and plug sending contacts l0, tip conductors of plug H and jack l5, lower back contact of jack |6, sleeve conductors of jack 4 and plug l3, receiving magnet I2, tip conductors of plug l3 and jack l4; and through the tip conductors of cord TTC and jack 2| to negative battery. When an operator at the switchboard inserts the answering plug 5| of a cord C in jack to answer the call, a circuit is closed from battery through the winding of relay 53, sleeve conductors of plug 5| and jack 50. over conductor 45, and winding of relay 24 at the test board; and relays 24 and 53 operate. The winding of relay 54 is connected through the ring conductors of plug 5| and'jack 50 to conductor 44 of the trunk T butrlay 54 does not operate since the middle contact of jack 2| at the test board is opened when the plug of a cord is inserted in this jack. The operation of relay 24 closes a circuit through the lower winding of relay 25. Relay 25 operates and closes a locking circuit through its upper winding and contact to ground at the upper contact of jack 2|. At its lower back contact, relay 25 opens the circuit over conductor 43, thereby extinguishing the answering lamps 41 at the switchboard. At its lower front contact relay 25 closes a circuit through the inner lower front contact of relay 26 for energizing the lower (locking) winding of relay 26. Relay 53 closes a circuit for operating relay 6|; and relay 6| connects ground through its inner front contacts to the lower windings of repeating relays 55 and 15. A circuit is thereupon traced from ground at the inner left front contact of relay 6|, windings of relay 55 in series, lower front contact of relay 53, tip conductors of plug and jack 50, over trunk conductor 42 to the test board, lower back contacts of relays 3| and 21, sleeve conductors of jack 2| and cord TTC, middle contact of jack I6, sleeve conductors of jack l5 and plug ll, sending contacts I0, tip conductors of plug II and jack [5, lower contact of jack 6, sleeve conductors of jack- 4 and plug I3, winding of receiving magnet l2, and through the tip conductors of plug l3, jack 4, cord TTC and jack 2| to negative battery. The junction point between the windings of relay 55 may at this time be connected through the spacing contact of relay 15 to negative battery or through the marking contact of relay 15 to positive battery; or the armature of relay 15 may be in mid-position with both contacts open. In any of these three cases the closure of the answering cord loop causes the energization of relay 55 to close its marking contact. The aforementioned operation of relay 6| also connects negative battery through its outer right front contact, inner backcontact of relay 13, and through the contacts of teletypewriter key 66 to the line side of the upper winding of relay 15. If the key 66 is operated, the sending cont-acts 80 and receiving magnet 8| are included in this connection. In either case relay 15 is energized to close its marking contact. The test board operator and answering switchboard operator may now communicate with each other by use of their teletypewriters, the signals being repeated by relays 55 and 15 in usual and wellknown manner. If connection is desired with a subscriber's loop or an outgoing telegraph line, the switchboard operator inserts the calling plug 1| in the jack of this loop or line. Relay 13 operates, thereby extending the connection from the upper winding of relay 15 to the tip of the plug 1!. The operation of key to its ring position closes a ringing circuit through the tip conductor of plug H.

If an operator at the switchboard wishes to communicate with a test board operator, the plug 5| or plug 1| is inserted in jack 56; and assuming the plug 5| to be used, relays 53 and 24 operate. Relay 24 closes the circuit for energizing the lower winding of relay 25. The operation of relay 25 closes a circuit for lighting the answering lamp 26. Relay 54 operates, over conductor 44 to ground at the upper contact of jack 2 I, and closes a circuit for lighting the answering cord supervisory lamp 52. When the test board operator answers the call by inserting the plug of a teletypewriter cord TTC in jack 2|, relay 54 releases and relay 26 operates. The release of relay 54 extinguishes lamp 52 and the operation of relay 26 extinguishes lamp 20.

If the test board operator is the first to disconnect, removal of the plug of cord TTC from jack 2| again closes the circuit over conductor 44 for operating relay 54 of the cord C to light the answering cord supervisory lamp 52. When the switchboard operator removes plug 5|. from jack 50, relays 53 and 24 release. relay 24 causes the release of relays 25 and 26.

If the switchboard operator is the first to disconnect, removal of the plug 5| from jack 5!] causes the release of relays 53 and 24 but relays 25 and 26 are held operated by the ground at the upper contact of jack 2|; the release of relay 24 connects ground through its back contact and the upper front contact of relay 26 to the lower back contact of relay 21, thereby maintaining a loop circuit through the teletypewriter at the test board. When the plug of cord TTC is removed from jack 2|, relays 25 and 26 release.

Assuming the connection between an operator at the switchboard and an operator at the test board to have been established through cord C and trunk T as hereinbefore described, and a transmission test of cord C being desired, the calling plug 1| is inserted in the call-test jack 49 with plug 5| remaining in jack 50. Relay 13 operates through sleeve resistance 48. At the test board, the send jack I6 is connected by patching cord PC to the send jack 23. The sending contacts IU of the test board operators teletypewriter are thereby removed from the signaling circuit over cord TTC and through plug 5| and repeating relay 55; and a sending circuit is traced from negative battery at the upper back contact of relay 21, through the tip conductors of jack 23, cord PC, jacks l6 and I5 and plug I, through sending contacts In, sleeve conductors of plug ll, jacks l5 and I6, cord PC and jack 23, upper back contact of relay 3|, over conductor 4|, tip conductors of jack 49 and plug 1|, contact of key 10, lower front contact of relay 13, contacts of key 60 (and through magnet 8| and sending contacts 86, if key 66 is operated) to the line winding of repeating relay 15. Any signals sent by the contacts |ll over the calling cord loop are repeated by relay over the answering cord loop to the receiving magnet l2; in this manner the operation of repeating relay 15 is tested. By operating the recall-reverse key 30, the reversing relay 3| is operated through the lower contact of this key, the upper front contact of jack 23 and the normally closed contact of the bias jack 22. Relay 3| interchanges the connections between conductors 4| and 42 and the jacks 2| and 23 so that signals from contacts H] are transmitted over conductor 42 in the answering cord loop and are repeated by relay 55 over the calling cord loop to the receiving magnet l2; in this manner the operation of repeating relay 55 is tested.

To make a. bias test of the cord repeating relays 55 and 15, the test board operator inserts the plug of a test cord TC in the bias jack 22, and operates the test key l8 thereby connecting the voltmeter [1 to the contacts of relay 35. At the normally open contact of jack 22, a circuit is closed for operating relay 21. With relay 21 operated, the right (biasing) winding of relay 35 is energized and a circuit is closed from the source 29 of ZO-cycle ringing current, through the uppermost front contact of relay 21 and upper winding of inductance coil 28 to ground. Polarized signals are thereby induced in the lower winding of inductance coil 28 and transmitted through the inner upper front contact of relay The release of 21, lower contact of jack 23, upper back contact of relay 3|, over conductor 4| to the calling cord repeating relay 15. These signals are repeated by relay [5 through the answering cord, over conductor 32, through the lower contact of relay 3|, left winding of relay 35, to negative battery on the tip conductor of jack 2|. The contacts of relay 35 are thereby controlled by the repeated 20-cycle test impulses to alternately reverse the current through the voltmeter H. The voltmeter directly indicates the per cent bias introduced by relay '15, for instance, a reading of volts indicates 10 per cent bias. By operating the key 30 the impulses are transmitted over conductor 42 to relay 55 and the repeated impulses are received over conductor 4!, in which case the voltmeter indicates the bias introduced by repeating relay 55.

To test the recall-release feature of the cord C, the connection is established with answering plug 5! in jack 5! and the plug of the teletypewriter cord TTC in jack 2! The momentary operation of the recall-reverse key 30 closes a circuit through the lower winding of relay 32; and relay 32 looks through its upper winding to ground at the front contact of relay 24. Relay 3! does not operate since there is no plug in either of jacks 22 and 23. At its outer front contact relay 32 connects the interrupter 33 to conductor 44 to alternately operate and release the supervisory relay 54. The supervisory relay M is also alternately operated and released if plug H is in jack t9. Lamps 52 and T2 are flashed until the switchboard operator momentarily operates the key It! to its recall-release position. Ground is thereby connected through the uppermost front contact of relay 54 and the left contact of key 10 to the sleeve of jack 5%, shortcircuiting and thereby releasing relay 24. The release of relay 24 causes the release of relay 32 to end the flashing signal. With plug H in jack 50, the operation of key "IE! to its recall-release position connects ground through the uppermost contact of relay l4 and the right contact of key 10 to the sleeve of jack 50 to short-circuit and thereby release relay 24.

What is claimed is:

1. In a telegraph system, an operators position, cords arranged for repeating telegraph signals, a test board, and a trunk interconnecting said position and test board, said trunk being arranged for two-way communication and for testing the cords at said position.

2. In a telegraph system, an operators position, cords arranged for repeating telegraph signals, a test board, a trunk interconnecting said position and test board, and means at said test board comprising a ringing current generator connected to said trunk for testing the cords at said position.

3. In a telegraph system, subscribers lines, a switchboard comprising a link for use in completing desired connections, a test board, a trunk interconnecting said switchboard and test board, said trunk being arranged for two-way communication and for testing said link.

4. In a telegraph system comprising a switchboard and a test board, a trunk arranged for two-way communication between said boards, a link at said switchboard for use in completing desired connections, signal repeating means in said link, and means comprising said trunk for testing the signal repeating means of said link.

5. In a telegraph system comprising a switchboard and a test board, a trunk arranged for twoway communication between said boards, a link at said switchboard for use in completing desired connections, signal repeating means in said link, and means comprising an alternating current generator connected to said trunk for testing the signal repeating means of said link.

6. In a telegraph system comprising a switchboard, and a test board, a two-way trunk between said boards, a link at said switchboard for use in completing desired connections, a signal repeating relay in said link, means at said test board for sending signals over said trunk to said link and for receiving the repeated signals over said trunk from said link, and a voltmeter connected to said signal receiving means for indicating the bias introduced by said signal repeating relay.

7. In a telegraph system comprising a switchboard and a test board, a two-way trunk between said boards, a link at said switchboard for use in completing desired connections, supervisory signal means in said link adapted for intermittent operation as a recall signal, means in said trunk for causing the intermittent operation of said supervisory signal means, and recall-signal release means for said link.

8. In a telegraph system according to claim 7, means in said trunk responsive to the operation of said recall-signal release means for rendering ineffective said means for causing the intermittent operation of said supervisory signal means.

9. In a telegraph system comprising a switchboard and a test board, a trunk arranged for two-Way communication between said boards, a teletypewriter at said test board comprising sending contacts and a receiving magnet, means comprising jacks for connecting said sending contacts and said magnet in series with one of the conductors of said trunk for half-duplex signaling over the trunk, and means comprising said jacks for connecting the receiving magnet in series with said one of the conductors of the trunk and for connecting the sending contacts in series with another of the conductors of said trunk for full duplex signaling over the trunk.

10. In a telegraph system comprising subscribers stations, a switchboard and a testboard, a trunk between said boards for use in communicating between said boards, links at said switchboard for use in connecting subscribers stations, each of said links comprising repeating relays for repeating signals between interconnected stations, and means comprising said trunk for testing the operation of the signal repeating relays of any of said links.

TOLA A. MARSHALL. 

